The principal activity of this grant is to improve the care and treatment of children with cancer by participating in the Pediatric Oncology Group (POG). The three specific goals of the participation of the Dana-Farber Cancer Institute/Children's Hospital (DFCI/CH) and Maine Children's Cancer Program (MCCP) are to 1) enter and follow children with malignancies on appropriate Pediatric Oncology Group (POG) protocols 2) provide leadership in planning and executing POG protocols and 3) provide pilot clinical studies and scientific leadership to POG. 1) Patient entry: the referral patterns at the two institutions has not changed and the commitment to POG protocols remains high. Therefore, patients accrual will continue at the high level previously noted over the last grant period. 2) Leadership within POG: Drs. Weinstein and Grier respectively are the disease chairs for the Myeloid and Sarcoma Committees. The disease committee chairs have primary responsibility for all scientific and clinical activities within POG. Investigators from these institutions are currently or were in the last cycle chairs for 7 separate POG protocols and co chairs of 35 more. They also have 18 positions on disease or discipline committees within POG. Enthusiasm remains strong, and involvement at the current level will continue. 3) Pilot POG protocols and scientific leadership: Scientific leadership is detailed in part above. Dr. Arceci provided scientific leadership for and analyzed the samples of the MEC protocol (#9222) that piloted the use of multidrug resistance reversal agents (cyclosporine) in relapsed AML. This protocol provided the background for the about to open group wide AML up-front protocol (#9394) that will randomize whether or not patients will receive cyclosporine during maintenance therapy. DFCI ALL protocols have provided the background for one of the arms of the proposed new T- cell protocol (#9404). In addition, the background for the current stereotactic protocol (#9373) was in part developed at the Joint Center for Radiation Therapy and the DFCI. Finally, POG has embarked on a major effort to study the autologous transplant protocols for ALL (#9421) developed at the DFCl. Finally Dr. Lipshultz ran at DFCI/CH the pilot studies of late cardiac toxicity from anthracyclines that provides the background data for the randomized trial of enalapril for patients with elevated after load.